1a. Objectives (from AD-416):
To characterize experimental Nebraska-adapted hard white wheats in terms of tolerance to preharvest sprouting, and to determine whether DNA markers may be used as an alternative means of selection for the trait.

1b. Approach (from AD-416):
Five genetic populations, each composed of approximately 100 recombinant in-bred lines (RICLs), have been developed. Each involves matings of the keystone sprouting tolerant cultivar RioBlanco, and hard white wheat experimental breeding lines or cultivars adapted to Nebraska. These populations are grown in an augmented design, along with several hard red and hard white check cultivars. In the augmented design, individual RICLs are un-replicated, but randomly assigned to blocks; check cultivars are planted within each block, and used to provide an experiment-wise error estimate. The experiment has been grown in 2008 harvest years, and will be seeded for observation and data acquisition again in September, 2008. In addition, all hard white wheats from the University of Nebraska wheat breeding program, advanced from the 2008 NIN, TRP and DUP nurseries, will be included. Sprouting tolerance is assessed by snapping heads after before harvest maturity, drying in a greenhouse, and storing at –20 C until assayed in a misting chamber. DNA markers, derived from literature and database searches, will be used to test their utility as an alternate means of selection. After the 2009 data collection, sprout-tolerant hard white winter wheats will be selected and entered in USDA-ARS regional nurseries for testing of disease responses and agronomic performance.

3. Progress Report:
Tolerance to pre-harvest sprouting was assessed in Nebraska-adapted winter wheat cultivars and advanced white wheat experimental lines over multiple harvest seasons. A cultivar ranking system was developed, with results distributed to Nebraska-based scientists and extension personnel. The hard red winter wheats Camelot, Niobrara, Wesley and Jagalene consistently ranked amongst the most tolerant. Nuplains and Danby scored highest amongst hard white wheats. Experimental breeding lines from the University of Nebraska wheat breeding program also were assessed, and tolerant materials identified. In addition, sprouting tolerance was evaluated in more than 600 USDA-developed hard white breeding lines, and tolerance to pre-harvest sprouting correlated with previously identified DNA markers for the trait. DNA markers on three chromosomes were correlated with enhanced tolerance in four different wheat breeding populations. In three of four populations, a gene derived from the hard white wheat cultivar Rio Blanco was found to be consistently associated with enhanced tolerance. Rio Blanco is a keystone white wheat cultivar, contributing genes to much of the current Great Plains hard white winter wheat gene pool. Selection for DNA markers linked to the Rio Blanco derived gene (known as 3AS-PHS) will assist breeders in the development of future sprout tolerant hard white winter wheat cultivars. Two advanced breeding lines carrying the 3AS-PHS gene were released to wheat breeding programs via the USDA-ARS coordinated Northern Regional Performance Nursery.
An additional study investigated the capacity of red wheats to donate genes for sprouting tolerance to the white wheat gene pool. Crosses were made between panels of hard red and hard white wheats; subsequently, USDA-ARS developed automated seed sorting technology was used to produce pure white seeded populations for the analyses. After two harvest seasons, the red wheats Niobrara, Jagalene, and NE98466 were identified as carriers of genes capable of enhancing tolerance in hard white wheat backgrounds. Recombinant inbred (progeny) lines each from populations were developed by crossing these three red wheats to the high-yielding but susceptible hard white wheat NW99L7068. These materials were harvested in 2012 from plantings as Mead, NE and will be used to identify the new genes. The recombinant inbred lines also will serve as breeding materials for the selection of new high yielding sprout tolerant hard white wheats for possible cultivar release.